1. Field of the Invention
This invention relates to a method of preventing tars and asphalts and related materials from sticking to paving equipment. The method comprises 1) coating a paving equipment surface by spraying, rolling or brushing with a release agent, 2) adding or contacting asphalt, tar or related material to the equipment or otherwise handling or using the asphalt with the sprayed equipment, and 3) if transportation or movement of the asphalt or tar is the desired purpose of utilizing the paving equipment, separating the asphalt from the equipment by releasing it at its point of intended use or 4) otherwise releasing the asphalt or tar or related material from the paving equipment. The particular release agents envisioned by this invention comprise a concentrate which can be diluted, the concentrate comprising a fatty acid amide or mixture of fatty acid amides, a fatty acid neutralized with diethanolamine or another alkyl- or alkanolamine or amines, and an optional solvent or solvents.
2. Prior Art
It is well-known in the industry that asphalt tar and related materials, used in their molten or liquid state, have a strong tendency to adhere to surfaces of the equipment used to handle, transport and otherwise use them. This buildup can be severe, rendering the equipment completely unsuitable for its purpose.
One traditional way to address this problem has been to spray the equipment with diesel fuel, which forms a lubricating layer in between the asphalt and the equipment. However, for regulatory reasons, this has become an obsolete method.
One response to the regulatory pressure to stop using diesel fuel has been to use other, less environmentally-unacceptable alternative solvents. An example of this type is "004", a citrus-based solvent sold by the Pure Corporation. It is used to clean paving equipment and to prevent tar or asphalt from sticking to the equipment in the first place. This type of solvent suffers from several drawbacks, at least one of which is the increased cost compared to diesel fuel.
Another drawback is that frequently the solvents chosen have a detrimental effect on the asphalt or tar in its final location, leading to a decreased strength of the resultant surface. For this reason, most such solvents can not be approved by state departments of transportation (DOT) for use as truckbed release agents, and so cannot be used on truckbeds that are carrying asphalt to pave on state roads.
Typically, the tests are rather severe, allowing contact between asphalt and solvent for 24 hours, and determining if there is any discoloration whatsoever in the solvent mixture. Most solvents used for release agents are unable to pass such a test.
Another response has been to utilize water-dilutable formulations. The solvent in this situation is water, which is cheap and plentiful, and known to repel asphalt. However, these materials suffer from serious drawbacks, leading to a reputation in the industry that they are ineffective.
The major drawback is that the water film is insufficiently persistent. This is caused primarily by the fact that the viscosity of water and many water solutions is very low, leading to the film rapidly draining off of the equipment, rendering it unprotected once again. The other drawback is that the water tends to evaporate, and the materials currently on the market are sufficiently poorly formulated that their is no residual film after the water dries.
U.S. Pat. No. 5,407,490 (Zofchak) discloses a method for releasing blacktop or other sticky materials from a truck bed, utilizing a concentrate comprising alkyl esters and surfactants. The concentrate is diluted in a ratio of about 20-30 to one with water, and applied to truck beds.
Since the method involves use of a solvent, namely alkyl esters, and dilution with water prior to application, it is essentially a combination of the two responses outlined above. It uses a solvent, but dilutes the concentrated solvent mixture with water prior to applying.
However, most solvent mixtures suffer from the drawbacks mentioned above, and so most state DOTs would likely not approve of the use of such a mixture. Therefore, a method of utilizing water as a diluent that does not utilize solvents that attack asphalt is desired.
Similarly, Vitech SOR, a synthetic hydrocarbon, is offered by Vitech International as a formulation component for an asphalt release agent. It is typically formulated with a small amount of a surfactant to render it emulsifiable, and diluted with water at a ratio of 1 part concentrate with 10 to 30 parts water.
This material is also a combination method, employing a solvent, an emulsifier system and water. Therefore, it will also likely not be approved by State DOTs.